To demonstrate this is no flash in the pan with more than 1000 made in 2015, and 250 in active service throughout 11 European countries, including in the UK, as it aims to ramp up its production to 10,000 hydrogen-powered ix35s. We have even tested the technology by running one on our own long-term fleet to see how feasible it really is.

The 2007 Tucson-based prototype had a 100kW fuel cell, a 152-litre gas tank, a 93mph top speed and a 186-mile range. Today’s car, based on the ix35 SUV has a 100kW fuel cell equivalent to 134bhp, a 144 litre of hydrogen capacity in two tanks, a 100mph top speed and a range of 369 miles.

Getting under the ix35 Fuel Cell’s skin

The fuel, compressed hydrogen at a pressure of 700 bar, is housed in two gas cylinders in place of a conventional petrol tank – a smaller 40-litre unit in front of the rear axle and a 104-litre tank behind the rear axle.

A fuel cell is mounted under the bonnet. The hybrid battery packs are located under the vehicle, positioned in the centre for weight distribution. Inside the fuel cell, an anode and cathode sandwich, and a polymer electrolyte membrane.

When the hydrogen flows over the anode, it splits into hydrogen protons and electrons. The polymer electrolyte membrane only allows the protons to pass through. The electrons travel to an external circuit which operates the motor. At the cathode, electrons and protons react with oxygen from the air to create water as a by-product of the process. Hyundai claims the driving range is 369 miles on a tank of gas.

The compact SUV uses 0.95kg of hydrogen to cover 62 miles and has a maximum tank capacity of 5.64kg of gas. The front wheels are driven by a 65kW - equivalent to 87.2bhp - electric motor, through a single speed reducer gear.

Under the floor is a 24kW battery developed by LG Chemicals, which is used primarily to assist the fuel cell stack when power demand is at its greatest. The battery pack is also used to ‘harvest’ waste energy from the regenerative braking system.

A blue-tinged Hyundai emblem provides another hint that this is no ordinary ix35. On the instrumentation panel, the dial on the left indicates ‘charge’ and ‘power’ to show when you’re expending the available electricity and when you’re recouping it through regenerative braking.

The right-hand dial shows your speed and remaining fuel level. There’s no noise on start-up, or thereafter, and step off from a standstill is impressively brisk, with 221lb ft of torque instantly on tap. Not that the performance is barnstorming; at more that 100kg heavier than a regular ix35, it is more than 1.5sec slower than a 2.0-litre diesel to 62mph, and maxes out at about 100mph.

Still, it feels perfectly comfortable to drive in the urban environment for which it is mainly intended. In contrast, the Nissan Leaf - arguably the best of the plug-in bunch - will manage just 130 miles before its battery is exhausted.

Thanks to their forever depleting batteries, running the ancillary electrical devices on most EVs is effectively like shooting a hole in your fuel tank, but the FC’s onboard generator makes running the air conditioning full blast seem relatively painless.

The fuel filler has a very thin, needle-type nozzle, so there’s no prospect of absent-mindedly pumping 30 litres of derv into your tank. Cleverly, the filler also includes infra-red technology to enable it to 'communicate' with the hydrogen fuel pump so that rate of flow and pressure can be regulated. The toughened hydrogen tanks impinge slightly on available luggage space, which is 436 litres with the rear seats up compared with the 591 litres of the regular crossover.

OK, the Fuel Cell will never be an engaging drive, but as a way of criss-crossing cities, it promises to be highly impressive. Hyundai expects the fuel cell to ‘last the life of the car’, but admits that the longevity of the unit is affected by both the purity of the hydrogen used and by the local air quality. The latter issue is tackled by the use of super-efficient charcoal air filters.

The fundamental issue with hydrogen-powered cars is still the chronic lack of the infrastructure required to refuel them, however HyFive is set deploy three more hydrogen re-fuelling points in London by the end of this year, taking the total in the capital to five.